The present invention relates to reduction of harmonic distortion and intermodulation distortion in a light emitting or laser diode and more specifically to a circuit and method that reduces third order intermodulation distortion by substantially matching the forward non-linear conductance characteristics of a compensating diode and the light emitting or laser diode.
In U.S. Pat. No. 4,032,802 an apparatus is disclosed employing a compensating diode and a light emitting diode connected in parallel for D.C. biasing and in anti-series with respect to an A.C. signal source. The patent asserts that the non-linear junction capacitance of the LED is responsible for the undesirable harmonic distortion and intermodulation products. To reduce distortion problems, a compensating diode matching the LED as nearly as possible with respect to capacitance characteristics is selected, with the bias points of the diodes being adjusted to equalize the effects of the diode capacitances.